ZFR1800 Series Wireless Field Bus System Technical Bulletin 71
• The ZFR1800 Series Wireless Field Bus devices transmit data using several
short messages that are collected and reconstructed at the destination. These
smaller messages can transmit between the larger WiFi messages. The short
messages have less chance of colliding with other messages and a better
chance of transmitting successfully. If a piece of the ZigBee wireless message
is transmitted at the same time as a WiFi message, it retries until it can transmit
at the next available gap (Figure 24).
Other wireless systems should not interfere with the ZFR1800 wireless system for
the following reasons:
• Cell phones do not operate on the 2.4 GHz ISM band; therefore, cell phone
transmissions should not interfere with the wireless Metasys systems.
• When a wireless system encounters WiFi transmissions in the 2.4 GHz
ISM band, most of the transmissions appear merely as noise, with insignificant
or no impact on wireless system communication.
• Wireless interference and transmission failures are minimized by maintaining
an adequate distance between wireless transmitting devices. If a wireless
device operating at 2.4 GHz (for example, a WiFi access point) with a standard
antenna is located at least 3 m (10 ft) from the ZFR1800 components, there
should not be any interference. Likewise, if a wireless device with a high-gain
antenna is located at least 6 m (20 ft) from a wireless Metasys system, there
should not be any interference.
• Tests indicate that WiFi channel 11 transmissions should not significantly
interfere with a wireless system unless the WiFi access points are within 3 m
(10 ft) of the wireless Metasys products, and the access points are transmitting
at full power almost continuously.
Figure 24: Message Transmission
IEEE 802.15.4
ZigBee
WiFi
IEEE 802.11
FIG:collide
Message B
Message C
Collision
Transmission
Retry
Success
Message A
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